docs: def guess_fileformat(aUri):
      """
      Simple file format guessing (using rdflib format types) based on the suffix
  
      see rdflib.parse [https://rdflib.readthedocs.org/en/latest/using_graphs.html]
  
      """
      if aUri.endswith(".xml"):
          return "xml"
      elif aUri.endswith(".nt"):
          return "nt"
      elif aUri.endswith(".n3") or aUri.endswith(".ttl"):
          return "n3"
      elif aUri.endswith(".trix"):
          return "trix"
      elif aUri.endswith(".rdfa"):
          return "rdfa"
      else:  # to be handled outside this method
          return None